For the purpose of extracting air effectively from fluid which passes through the reservoir of a hydraulic system at elevated rates of flow, it has been proposed to position a fine-mesh net structure between two mutually opposite corners of the reservoir, with the net structure arranged in an inclined position.
The results of trials carried out with the aid of such a net structure have shown that, in addition to flow rate, the ability to separate air effectively from hydraulic fluids is also contingent on the viscosity of the fluid concerned, the angle at which the net structure is inclined and the fineness of the mesh.
Since in the case of closed systems the oil, or hydraulic fluid, will pass through the net structure several times, air separation will approach a final value asymptotically. This final value will be higher with increasing mesh fineness, since the air bubbles are divided in accordance with size.
Consequently, in order to separate air effectively, it is necessary to use a net of vary fine mesh. However, the pressure drop across fine-mesh net structures is higher than in other cases, particularly when cold-starting mobile hydraulic systems, in which a small reservoir is desirable for several reasons. In practice, the high viscous fluid therethrough, a situation which is quite normal with the cold-start of hydraulic systems, will result in problems of such gravity that other solutions must be sought.
Those solutions proposed hitherto, however, have been both expensive and complicated and have not taken into account the fact that a fine-mesh net structure constitutes and effective means for separating gas from a continuously operating hydraulic system, i.e. subsequent to solving cold-start problems.
Solutions hitherto proposed which recommend the use of different types of pressure limiters comprising moveable components can cause cavitation problems and result in unsatisfactory gas separation.